1. Field of the Invention
This invention pertains to an improved internal heat exchange system significantly reducing the energy consumption of refrigerator/freezer units that use nonazeotropic refrigerant mixtures as working fluids. Specifically, liquid refrigerant leaving the condenser of a multi-compartment refrigeration system is subcooled prior to entering the evaporator on the way to a compressor. The efficiency of subcooling is improved by placing the working fluid mixture in heat exchange relationship with the cold suction vapor on route from the evaporator to the compressor and in heat exchange relationship with the evaporating fluid in the evaporator over the length of the evaporator.
2. Background of the Prior Art
Conventional refrigerator/freezer units employ a single refrigeration cycle to cool both the refrigerator and freezer, which are maintained at sharply different temperatures. Such refrigeration systems typically include a condenser and a compressor, between which working fluid is circulated, the condenser and the evaporator being separated by at least one heat exchanger, and at least one evaporator. In certain systems, multiple heat exchangers and evaporators can be used.
To conserve energy, and improve efficiency of the system, it is conventional to subcool the working fluid leaving the condenser, prior to entering the expansion valve or other means for expanding the gas flow at the entry to the evaporator. U.S. Pat. No. 4,773,234, Kann, U.S. Pat. No. 4,577,468, Nunn et al and U.S. Pat. No. 4,285,205, Martin et al all disclose this type of subcooling, where the liquid leaving the condenser is passed in heat exchange with suction gas leaving the evaporator. A typical system, such as that described in Martin et al, is illustrated in FIG. 1. The working fluid leaving the condenser passes, at point 100, in heat exchange relationship with a suction gas exhibiting the evaporator 102. The location of the heat exchange is not critical, save that it lie between the condenser and expansion valve 104, or similar expansion means, immediately upstream of the evaporator.
Conventionally, working fluids for systems of this type employ a single refrigerant, such as R12. U.S. Pat. No. 4,781,738, Fujiwara et al, as well as others, employ nonazeotropic refrigerant mixture working fluids in systems of this type. In general, it is known that nonazeotropic mixtures can be used in multi-compartment refrigeration systems, that is, refrigeration systems wherein at least two compartments are maintained at separate temperatures.
Nonetheless, superior efficiencies in subcooling the working fluid leaving the condenser may be of value in improving the efficiency of systems of this type.